The present invention is related to a process for forming spheroidal-like particles from a water-wet mixture of materials, at least one of which is hydratable. The process involves allowing the mixture to be formed into spherical particles in a spray tower. The chosen forms are then cooled to a temperature sufficiently low so that the hydratable material is hydrated. The material is heated to a temperature which allows the water of hydration and free water to be driven off. This process allows for the elimination of the need for further size reduction and the associated dust.
Dry mixtures of materials are desirable in many different situations. Included among these situations are the inclusion of a solid diluent with such materials as a dry peroxyacid compound, a surfactant compound, a dry fertilizer material or an enzyme. These materials are only a few of the many which may be benefited by the present process's ability to: (1) form particles which are quickly dried; and (2) form small particles without the usual inherent dustiness associated with such formation.
The prior art contains many references which disclose compositions containing mixtures of hydratable materials with nonhydratable materials. Most such references, however, are not concerned with utilizing the hydratable materials as a drying aid and, hence, do not address the favorable and unfavorable aspects of such use. One reference which does disclose the use of a hydratable material as a drying aid is U.S. Pat. No. 3,770,816, to Nielsen, issued Nov. 6, 1973. This reference, while disclosing the use of a hydratable material to dry a nonhydratable material, diperisophthalic acid, does not disclose that the drying process has critical parameters which must be controlled. U.S. Pat. No. 4,091,544, to Hutchins, issued May 30, 1978, while disclosing that the drying process has critical parameters which must be controlled, does not disclose critical parameters for spray hydration operation of such mixtures. Notwithstanding the teachings of Hutchins, those skilled in the art for years used expensive liquid carbon dioxide (CO.sub.2) in spray tower hydration operations to reduce the temperature of the particles 25.degree.-30.degree. C. below the hydration temperature, believing that the colder the air inlet temperature the better the hydration process. The use of CO.sub.2 was not only costly, but processing also caused problems in spray hydration operations.
It is, therefore, an object of this invention to provide a superior process for the spray hydration of a mixture of hydratable and nonhydratable materials in a spray tower.
It is also an object of the present invention to optimize the hydration of the particles.
Another object of the present invention is to reduce cost by eliminating the need for liquid CO.sub.2 to cool spray tower inlet air, etc.
Still other objects are to make hydrated particles which are easy to handle and which are chemically stable.
These and other objects of the present invention will become apparent from the following disclosure.
All percentages and ratios used herein are by weight unless otherwise specified.